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1997 Forest Insect and Disease Conditions for the Southern Region

Note: bold hypertext links within the narratives (e.g., Dogwood anthracnose) will take visitors to the on-line publication, The Health of Southern Forests which displays additional graphics and discusses the biology and southern history of the causal agent in more detail. Not all causal agents are linked. Non-bolded links provide for within-document navigation.

Most Significant Conditions in Brief

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As predicted in the 1996 report, carryover from the 1995 and 1996 weather and climate-related occurrences affected the health of southern forests in 1997. Most notably, southern pine beetle populations in eastern North Carolina increased dramatically in areas previously stressed by Hurricanes Fran and Bertha. In Florida, pine engraver populations sharply increased in response to an opposite weather-based stressor -- drought. Damage was most severe in thinned stands in the north central part of the state. The good news on European gypsy moth continued into 1997. There again was no noticeable defoliation in Virginia -- an apparent continuing after effect of the Entomophaga fungus outbreak which virtually wiped out the insect throughout its eastern range last year. Meanwhile, the European gypsy moth's cousin, the Asian gypsy moth, has now been officially declared eradicated in North Carolina, where a 1993 introduction was once reason for grave concern. The hemlock woolly adelgid continues its relentless spread down the Appalachian chain, much to the chagrin of entomologists and forest ecologists who recognize the vital role hemlock plays in the unique ecology of the region.

Perhaps less spectacular, but no less insidious and destructive, are the forest diseases. Dogwood anthracnose, and butternut canker continued to intensity throughout their range, and losses to fusiform rust littleleaf disease, and annosus root disease continued at endemic, though highly significant levels. Oak decline syndrome continues to cause significant losses at various locations throughout the South.

Status of Forest Insects

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Balsam woolly adelgid, Adelges picea, on Fraser fir in No. Carolina, Tennessee, and Virginia.

Fraser fir has a very limited range in the Southern Appalachians, and appears almost exclusively in pure stands on the highest mountain peaks or in combination with red spruce at somewhat lower elevations (Figure 1. GIF 49K ). Since the first introduction of the balsam woolly adelgid , approximately 64,700 acres of Fraser fir have been affected. The insect will attack trees of all age classes, but prefers the older fir trees. Adelgid populations were again high in 1997.

Black turpentine beetle, Dendroctonus terebrans, on southern yellow pines regionwide.

Black turpentine beetle activity was at normal, levels throughout the South. The insect is most evident in trees stressed by logging injury, root compaction, and similar stressors.

Buckmoth, Hemileuca maia, on various oaks in Louisiana

The buck moth population in and around federal historical districts in New Orleans appears to be on the rise again.

Cypress looper, Anacamptodes pergracilis, on baldcypress and pond cypress in Florida.

Although very little defoliation by this insect was evident anywhere in 1996 (following the widespread outbreak of 1995), high populations reappeared in the summer of 1997 in Glades County, causing noticeable (>30%) defoliation over 15,000 acres.

Fall cankerworm, Alsophila pometria, on various hardwoods in North Carolina.

Within the City of Charlotte, high populations of the fall cankerworm have been present since 1987. Natural controls, which regulate outbreaks in uninhabited forests, have not been effective in reducing fall cankerworm populations in this urban environment. Charoltte has a large number of mature willow oaks that provide an almost unbroken canopy over much of the city. Survey results from stick ban traps indicate that heavy defoliation is again expected in the spring of 1998. To prevent defoliation and maintain the health of urban trees, the city proposes to treat approximately 5,850 acres with the biological insecticide Bacillus thuringiensis in the spring of 1998.

Forest tent caterpillar, Malacosoma disstria, on oaks, tupelo gum, and other hardwoods in Florida, Louisiana, and North Carolina.

The outbreak of forest tent caterpillar in west central Florida, which began in 1994, continued to persist, expand, and in places, dramatically increase or decrease in intensity during the spring of 1997. Severe levels of defoliation to primary hosts (i.e., water, laurel, and live oaks) was more prevalent and widespread than in preceding years in portions of Highlands, Manatee, Orange, Osceola, Pinellas, and Sarasota Counties. Outbreaks were especially troublesome in urban areas of Bradenton, Kissimee, Sarasota, and St. Petersburg. Long-standing outbreaks subsided in portions of Hardee, Hillsborough, and Polk Counties. Mass emergence of larvae from overwintering egg masses in early February was notably earlier than the March emergence of previous years, presumably due to a mild winter and corresponding early spring foliage flush.

In Louisiana, over 230,000 acres of primarily tupelo gum were defoliated in forested wetlands. St Charles, St. John the Baptist, Ascension, and Livingston parishes were affected.

In North Carolina, the forest tent caterpillar defoliated an estimated 25,000 acres along the Roanoke River near Williamston. The Houston, Texas (Harris County) area also experienced an outbreak in 1997, possibly brought on th 1996's dry weather followed by a wet spring.

Fruittree leafroller, Archips argyrospila, on bald cypress in Louisiana

The fruittree leafroller defoliated baldcypress over an area of 525,000 acres in southeastern and south central Louisiana. Although the predominant impact is loss of growth, repeated annual defoliation has resulted in significant crown dieback and mortality of sapling/pole-sized cypress. Jefferson, St. Charles, St. John the Baptist, Ascension, James, Lafourche, Assumption, St. Martin, Terrebonne, St. Mary, Iberia, /St. Martin, Iberville, and West Baton Rouge parishes were affected.

Gypsy moth (Asian), Lymantria dispar, on various hardwoods in North Carolina.

The isolated infestation that was discovered in 1993 at the Military Ocean Terminal at Sunny Point, North Carolina is now considered officially eradicated. No Asian gypsy moths have been trapped in the past two years.

Gypsy moth (European), Lymantria dispar, on various hardwoods in Alabama, Arkansas, Georgia, North Carolina, South Carolina, and Virginia.

No noticeable gypsy moth defoliation occurred in Virginia in 1997. This is the apparent continuing after effect of an Entomophaga maimaiga fungus epidemic that virtually wiped out gypsy moth populations throughout the eastern range.

In North Carolina, an isolated gypsy moth infestation was identified in and around the town of Highlands (Macon and Jackson Counties). An eradication project will be initiated in 1998.

Meanwhile, in Tennessee, male trap catches were the lowest since 1990. Nevertheless, a new infestation was discovered in Overton County. The 1996 Scott County infestation was reduced by 96% through aerial application of Bacillus thuringiensis.

Follow-up trapping continued on the 1993-95 gypsy moth eradication project in north central Arkansas. Only a limited number of male moths were captured. Although trapping will continue, no treatments are planned for 1998.

Treatments to slow the rate of spread of the gypsy moth continue to be implemented along the expanding front in the 7-million acre Gypsy Moth Slow-the-Spread (STS) Pilot Project area in the states of North Carolina, Virginia, West Virginia, and Michigan. During 1997, a total of 29,856 acres were treated as part of STS; 4,405 acres of private land in North Carolina, 18,457 acres of private land in Virginia, and 6,370 acres of private land in West Virginia, and 250 acres of national forest land in Virginia and West Virginia. About 63 percent of the area was treated with a biological insecticide, Bacillus thuringiensis, 37 percent with a mating disruptant specific to gypsy moth and 1 percent using mass trapping.

Hemlock woolly adelgid, Adelges tsugae, on hemlock in North Carolina and Virginia.

There were no additional counties infested in 1997, although hemlock woolly adelgid populations continued to build and intensify within the outbreak counties, with officials predicting noticeable increases in 1998. The insect threatens the entire range of eastern hemlock (Figure 2. GIF 43K), and is found throughout Virginia wherever hemlock is found in abundance. It is also found in four counties in Western North Carolina. The USDA Forest Service is working with the New Jersey Department of Agriculture to introduce a predacious beetle as a potential biological control agent.

Larger elm leaf beetle, Monocesta coryli, on mixed elms in Louisiana

The larger elm leaf beetle again affected approximately 3,500 acres of mixed elm in the Sherburne Wildlife management Area in Iberville Parish. Wildlife biologists reported some apparent mortality related to the defoliation.

Locust leafminer, Odantata dorsalis, on black locust throughout host range in region.

Locust leaf miner was particularly pronounced in 1997 along the Ohio River Valley in northern Kentucky and wherever its host was found along the Blue Ridge Parkway in Virginia and North Carolina. While the insect causes little if any permanent damage, it is unslightly, causing trees to turn brown, and in turn causing concern among many members of the public.

Nantucket pine tipmoth, Rhyacionia frustrana, on shortleaf and loblolly pine regionwide.

Tip moth damage was prevalent throughout the region, especially throughout the range of shortleaf pine. Damage was most pronounced on open grown trees. While the insect rarely causes mortality, it can cause significant growth loss on selected sites.

Orangestriped oakworm, Anisota senatoria, on various oaks in Florida.

Caterpillar populations of this late-season defoliator, which were noticeably present in 1995 and 1996, reached outbreak proportions over 300 acres of residential neighborhoods in NW Gainesville. Noticeable to complete defoliation was widespread on oaks, particularly laurel oak, but the biggest problem was the nuisance to homeowners created by the tremendous amojnts of frass and wandering hordes of caterpillars during September and October.

Pine engraver beetles, Ips spp. ,on southern yellow pine regionwide.

Three species of pine engraver beetles, Ips avulsus, Ips grandicollis, and Ips calligraphus, occur in the South.

In Florida, the incidence and magnitude of pine engraver infestations increased to significant levels from late October through December of 1997 throughout north and north central Florida following unusual and prolonged drought. Infestations were most severe in recently thinned stands.

Pine engraver beetle activity was also inordinately high in the piedmont areas of North Carolina, Virginia, and Georgia.

Pine sawflies, Neodiprion spp. , on various pine species in Florida, Louisiana, Texas, Tennessee, and Virginia.

In Florida, high populations of the redheaded pine sawfly (Neodiprion leconteii) continued to cause noticeable to severe defoliation to all ages of longleaf pine in the Seminole Springs area of Lake County. Scattered defoliation was also reported throughout east Texas by redheaded pine sawflies and black-headed pine sawlies, Neodiprion excitans.

Heavy defoliation by the loblolly pine sawfly (N. taedae taedae) was scattered across northern middle and west Tennessee. Defoliation of loblolly pines by the loblolly pine sawfly has occurred on approximately 3,000 acres, primarily in Caldwell Parish, with lesser amounts in LaSalle and Winn Parishes, Louisiana.

Severe, but scattered defoliation by Hetrick’s sawfly (N. hetricki) occurred over a 6 county area in Southeastern Virginia. One 30-acre pine plantation was treated to prevent defoliation.

Reproduction weevils, Hylobius spp., on slash pines in Alabama.

Seedling trees in a slash pine plantation in Mobile County were killed by reproduction weevils. Total area impacted amounted to about 20 acres.

Southern pine beetle, Dendroctonus frontalis, on southern yellow pine southwide.

In 1997, southern pine beetle (SPB) populations declined for the second consecutive year following the record-setting outbreak in 1995. In 1997, the number of infestations (spots) decreased by 30 percent (from 17.4 thousand to 12.1 thousand spots). However, the number of affected acres increased by 17 percent (from 7.3 million to 8.5 million acres). The number of beetle infestations decreased in Arkansas, Louisiana, Mississippi, North Carolina, Oklahoma, South Carolina and Tennessee. They increased in Alabama, Florida, Georgia, Texas, and Virginia. (Figure 3. GIF 19K).

Table 1. Southern Pine Beetle Infestations by State
1996 versus 1997
State 1996 1997 Percent
Alabama 2,023 3,273 61.80 %
Arkansas 3,603 292 -91.90 %
Florida 61 874 1,332.80 %
Georgia 702 1,415 101.60 %
Louisiana 968 830 -14.20 %
Mississippi 2,676 1,285 -51.89 %
N. Carolina 2,825 1,117 -60.50 %
Oklahoma 3 1 -66.60 %
S. Carolina 4,112 1,990 -51.60 %
Tennessee 185 114 -38.39 %
Texas 288 853 196.20 %
Virginia 50 91 82.00 %
Totals 17,496 12,135 -30.64 %


SPB populations started 1997 at extraordinarily low levels. In mid-summer, beetle populations made a dramatic comeback. There were outbreak populations along the coast of North Carolina, South Carolina, and Georgia; the Oconee National Forest (Georgia piedmont); north central Florida (Marion and Levey Counties); central and south Alabama; several of the National Forests in Mississippi; and east Texas. (Figure 4. GIF 45K ).

The 1997 outbreak in North Carolina was in the coastal plain in an area affected by Hurricanes Bertha and Fran in 1995. Many of the pines were stressed by the effects of salt-water spray and still have thin crowns. In Florida, the SPB outbreak is occurring in the north-central part of the state near Ocala. This is the southernmost documented range of SPB in Florida, and 1997 saw record-setting losses for the state. SPB killed nearly 8,000 acres, and the prediction is for continued problems. In Texas, SPB made a comeback after 2 years of low activity. During the month of August over half of the total infestations identified in the year were documented. The bulk of the spots occurred in the southeastern corner of the state. In all of the SPB outbreaks, active infestations were treated and pine beetle activity was closely monitored.

In 1997, there were federally funded SPB suppression projects on the National Forests in Texas, Mississippi, Alabama, North Carolina, Ouchita (AR) NF, Kisatchie (LA) NF, Ocala (FL) NF, and Chattahoochee-Oconee (GA) NFs, Alligator River (NC) NWR, and Dare County (NC) Bombing Range. There were cooperatively funded suppression projects in the states of Texas, Alabama, Mississippi, Arkansas, Florida, South Carolina, and North Carolina. It is anticipated that the number of suppression requests will increase in 1998.

Texas leafcutting ant, Atta texana, on southern pines and hardwoods in Texas and Louisiana.

This ant does not eat vegetation per se, but removes the foliage to its subterranean chambers where it uses it as a substrate on which it cultivates a fungus food. In 1997, it continued to defoliate pine plantations throughout east Texas and central Louisiana on sites with deep sandy soil.

Tussock moths, Orgyia spp. , on oaks in Florida.

Unusually high populations of tussock moth caterpillars were nearly as numerous as forest tent caterpillars in some locales of central Florida, contributing to widespread and extensive oak defoliation. High tussock moth caterpillar populations by themselves were a general nuisance in urban areas of Deland (Volusia County), particularly on the Stetson University campus during the spring of 1997.

Whitelined June Beetle, Polyphylla decemlineata, on slash pine in Alabama

An outbreak of whitelined June beetles killed 5 acres of slash pine seedlings in Mobile County. The slash pine was brought into Alabama from a Texas forest tree nursery. It is probable that the beetles were in the roots and/or duff used in seedling packing. The plantation was sprayed and will be check again in May-June of 1998 for survivors.

Status of Forest Diseases

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Annosum root disease, Heterobasidion annosum, on southern pines and eastern white pine.

Annosum root disease continues to cause significant losses throughout the South with mortality and growth loss ranging from 2-25% of growing stock on managed high risk stands (Figure 5 GIF 67K). The disease is most commonly associated with thinned pine plantations on sandy, well-drained sites, but can be found on a variety of sites, soils and forest conditions. Bark beetle infestations frequently occur within infected stands. In South Carolina, at least 1,500 acres of loblolly pine were salvaged as a result of annosum root disease infection in 1997.

Beech bark disease, Nectria coccinea var. faginata, on American beech.

Beech bark disease was not found in any additional counties, but the disease continues to intensify within the currently infected areas. Beech bark disease was first reported in the Great Smoky Mountains National Park in 1994. However, the first mortality reported in the South was reported as early as the mid-1980’s in northern Virginia. This is well outside the previously known distribution. Increases in the associated beech scale, Cryptococcus fagisuga, proliferation, continued in 1997. Figure 6 (GIF 41K) shows counties with confirmed infection centers.

Butternut canker, Sirococcus clavigigenti juglandacearan , on butternut.

This disease has been in the South for at least 40 years (figure 7 GIF 52K), and is believed to have killed 77% of the butternuts in North Carolina and Virginia. The fungus kills large trees, saplings, and regeneration. Trees exhibiting resistance have been found in Arkansas, North Carolina, Tennessee, Kentucky, and Virginia. A cove with a large number of canker-free and cankered trees in Western North Carolina has been converted to a seed collection area, with potentially resistant trees being propagated in an East Tennessee nursery. Butternut canker is expected to spread and kill most of the resource, including regeneration. The species will be replaced by other species on these sites (e.g., black walnut). It is too early to project the benefits of selection and breeding. In 1997, a few individual trees in North Carolina appeared to be recovering from the disease. The reason for the apparent recovery is unknown.

Dogwood anthracnose, Discula destructiva, on flowering dogwood in Kentucky, Virginia, North Carolina, South Carolina, Tennessee, Georgia, and Alabama.

Dogwood anthracnose is now found in 241 counties in the South (figure 8 GIF 57K). The disease is primarily found in the mountains, foothills, and upper Piedmont. Damage is most severe above 3,000 feet in elevation where all the flowering dogwoods are severely affected in cool shaded areas while trees in the sun are doing well. The fungus has spread to the upper Piedmont and part of the Coastal Plain, but the impact has been minor.

Dutch elm disease, Ophiostoma ulmi, on elm (particularly American elm) southwide.

Scattered to localized mortality continues to occur at generally low severity levels in urban and wild populations of elms.

Fusiform rust, Cronartium quercuum f. sp. Fusiforme , on southern pines southwide.

Fusiform rust is the most damaging disease of loblolly and slash pine sin the South. Other pine species may also be infected, but little damage or mortality occurs. An estimated 13.4 million acres of loblolly and slash pine have at least 10 percent of the trees infected. Georgia is the most heavily impacted, with 4.6 million acres (49 percent of host type) affected. In South Carolina, man young stands were prematurely harvested throughout the state because of heavy fusiform rust infection in 1997.

Littleleaf disease, Phytopthora cinnamomi, on loblolly and shortleaf pines in Alabama, Georgia, North Carolina, South Carolina, Tennessee, and Virginia.

Littleleaf disease continues to cause growth loss and mortality across the Piedmont areas of the affected states. Shortleaf pine is highly susceptible while loblolly pine is affected at a later age. Many of the stands that were converted from shortleaf to loblolly are now reaching the age of susceptibility. These stands are often attacked by bark .

Northern hardwood decline on eastern hardwoods, white conifers, and various bioindicator species in Virginia.

Investigations are underway in southern Virginia to determine the cause of reported mortality and dieback to the northern hardwood forest type at relatively high elevations near the Mt. Rogers area. While some have speculated that the cause is air pollution, results of the investigation at this writing are inconclusive. Preliminary surveys show less than 1 percent of the forest type affected.

Oak decline, abiotic and biotic influences, regionwide on oaks, hickories, and associated hardwoods.

Oak decline is a syndrome resulting in a dieback and mortality of dominant and co-dominant mature oaks. Causal factors are stressors such as drought, frost, defoliation by insects, and secondary insects such as Armillaria root disease and two-lined chestnut borer (Agrillus bilineatus). Host, age, and site conditions also play a role. Analysis of forest inventory data in 12 southern states shows that 3.9 million acres of upland hardwood forest are affected by oak decline -- about 9.9% of the susceptible host type. Average annual mortality volume of oaks on affected sites was 45 percent higher than on unaffected areas. Some of the oak decline reported is in areas previously heavily defoliated by the gypsy moth. Oak decline and gypsy moth interact; pre-existing oak decline increases mortality after gypsy moth defoliation. Also, severe defoliation can induce oak decline in previously unaffected areas. Also, severe defoliation can induce oak decline in previously unaffected areas. No new local or widespread occurrences of severe decline were reported in 1997.

Oak wilt, Ceratocystis fagacearum, on oaks (especially red oak group and live oaks) in Arkansas, Kentucky, South Carolina, Tennessee, Texas, and Virginia.

Oak wilt continues to be epidemic in central Texas with the number of affected counties remaining at 61. A cooperative oak wilt suppression project continues in the area. The U.S. Army Corps of Engineers has also implemented suppression efforts on recreational lands surrounding several lakes in central Texas. Oak wilt is endemic throughout the rest of the Southern Region.

Pitch canker, Fusarium subglutinans, on loblolly pine, longleaf pine, slash pine, shortleaf pine, regionwide

Pitch canker has returned to endemic levels after a major increase in 1995. Scatterred trees across the Region are infected, but impacts are minor.

Nursery Pests

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Damping- off, Fusarium sp. and Pythium sp., regionwide on southern pines.

Damping-off is the most common disease problem facing southern nurseries. Loss of seedlings to damping-off varies greatly from year-to-year owing to the interaction of pathogenic fungi (species of Fusarium, Pythium, Rhizoctonia, and Phytopthora) and environmental conditions. Seedling losses can be severe when germination is slow due to cold, wet weather. In 1997, over one-half million seedlings were lost in one South Carolina nursery due to this interaction of abnormal climate, Phytopthora, and Fusarium.

Lygus bug, Lygus spp., South Carolina on loblolly pine.

Seedling damage from Lygus bug feeding resulted in the loss of 60,000 loblolly pine seedlings in South Carolina.

Rhizoctonia needle blight on conifers regionwide.

Rhizoctonia needle blight destroyed about 250,000 longleaf pine seedlings at the Taylor Nursery in South Carolina.

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Seed Orchard Insects and Diseases

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Coneworms, Dioryctria amatella, Dioryctria clarioralis , Dioryctria disclusa, Dioryctria merkeli , on southern pine cones, regionwide.

Coneworms continued to cause damage in seed orchards across the South. Data from the Southwide Coneworm Survey indicated substantial populations of the three primary species: the webbing coneworm, Dioryctria disclusa, the southern pine coneworm, D. amatella, and the loblolly pine coneworm, D. merkeli. Impact was intensified due to a sparse cone crop for all pine species in 1997.

Insect pests of white oak acorns, Filbertworm, Cydia latiferreana, acorn weevils, Curculio spp., and Conotrachelus spp., acorn wasp, Valentinia glandulella, and gall wasps, Cynipoidea sp., on white oak acorns in Arkansas.

These insects are responsible for substantial destruction of the white oak acorn crop on monitored research plots on the Ouachita and Ozark National Forests. Acorn weevils and filbertworms are the primary pests of white oak in the areas studied.

Pitch canker, Fusarium subglutinans, on loblolly pine, longleaf pine, slash pine, and shortleaf pine regionwide.

Cone collection, storage, and seed extraction methods have been found to cause contamination of pine seeds by Fusarium subglutinans. The USDA Forest Service and Auburn University are examining some of these interactions in shortleaf and longleaf pines in hopes of developing strategies for increasing seed efficiency by reducing contamination.

Seed bugs, Leptoglossus corculus, Tetyra bipuctata, on southern pines regionwide.

Seed bugs continued to cause damage on loblolly, longleaf, shortleaf, and slash pine orchards throughout the South.

White pine cone beetle, Conopthorus coniperda, on white pine cones in Tennessee and North Carolina.

Overwintering white pine cone beetle populations increased over 1996 levels at the Digital Arborist Beech Creek Seed Orchard, the North Carolina Forest Service Edwards Seed Orchard, and three Tennessee Division of Forestry seed orchards.

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